AS Daily A Level Physics question
Two electric heaters each transfer 150 kJ of energy to identical beakers of water. Heater A takes 3.0 minutes; Heater B takes 2.0 minutes. Compared with Heater A, the power of Heater B is:
Answer
The correct answer is A.
Correct: A — 1.5 times as large. With the same energy transferred, power is inversely proportional to time, so PB/PA = tA/tB = 3.0/2.0 = 1.5. A — Matches the inverse relation with time: shorter time gives 1.5× the power. B — Treats power as proportional to time (2.0/3.0 ≈ 0.67), which reverses the inverse relationship. C — Assumes power simply doubles, ignoring the actual 3:2 time ratio. D — Ignores that delivering the same energy in less time must increase the rate (power).